It is a common practice to utilize aerial vehicles for measurement of various environmental parameters. Typical wind measurement devices onboard aerial vehicles, particularly helicopter or multi-rotors, are affected by the vehicle's body or propulsion systems, and therefore have a limited level of accuracy. Due to the high distribution and increasing utility of low-cost small and medium size aerial vehicles (UAVs), there are evident benefits to a compact, low-weight and accurate wind measurement device, capable of being carried by these type of vehicles. One of several possible applications is the external performance monitoring of wind-turbine power production. The ability to position the accurate wind measurement device according to the invention directly in front of wind turbine rotors enables wind resource characteristics (predominantly direction and speed) detected by the measurement instrumentation mounted on the wind turbines (the logged data of which are often biased due to the positioning of the instruments behind the rotor-blades) to be compared with the data taken by an external, unbiased device, mounted on an unmanned aerial vehicle. The device's better accuracy enables corrections to the alignment of the wind turbine nacelle towards the prevailing wind direction among other corrections, thereby optimizing power production. The scale, mobility and autonomous capabilities of unmanned aerial vehicles carrying the device enable scheduled, sporadic, unmanned and on-demand, external and unbiased power production performance monitoring of wind turbines. This enables constant monitoring and immediate or post flight corrections to the wind turbine alignment, all of which capabilities are currently non-existent and very much required.